Increased Belowground Carbon Allocation Reduces Soil Carbon Losses Under Long-Term Warming

Area of Science:

• Forest ecology
• Soil science
• Climate change science

Background:

• Forest soils store significant soil organic carbon (SOC).
• Global warming may accelerate SOC mineralization, releasing CO2 and creating a positive climate feedback.
• Alpine forests are particularly vulnerable to warming due to amplified temperature increases.

Purpose of the Study:

• To investigate the long-term effects of experimental soil warming on forest soil CO2 efflux and SOC dynamics.
• To determine the primary drivers of changes in soil CO2 efflux under warming conditions.

Main Methods:

• Experimental soil warming (+4°C) in a Northern Limestone Alps mountain forest over 18 years.
• Measurement of soil CO2 effluxes and soil organic carbon (SOC) stocks.
• Analysis of radiocarbon age of SOC and root respiration/production.

Main Results:

• Soil warming significantly and persistently increased soil CO2 effluxes (~13% per 1°C).
• SOC stocks showed a non-significant decrease, less than effluxes suggested.
• Increased root respiration was the primary driver of elevated CO2 effluxes.
• Increased root production and turnover likely replenished SOC.

Conclusions:

• Long-term soil warming enhances forest soil CO2 effluxes.
• Increased carbon allocation to the rhizosphere may partially offset carbon loss from SOC mineralization.
• Forests may exhibit a more complex response to warming than previously assumed.